How long is DNA? [2025 data]

A single human cell contains about 2 meters of DNA, while the entire human body contains roughly 6 billion kilometers of DNA—enough to span the Earth-Sun distance over 40 times

Dr. Matic Broz
Dr. Matic Broz
Computational chemist
How long is DNA? [2025 data]
Quick Answer
  • DNA in one human cell: ~2 meters (6.3 billion base pairs)
  • Total DNA in human body: ~6 billion kilometers (3.7 billion miles)
  • DNA compaction ratio: 10,000:1 to fit inside a 6 μm nucleus

How long is DNA in one cell?

The DNA in a single human cell stretches approximately 2 meters (6.6 feet) when fully extended. This figure comes from multiplying the distance between base pairs (0.34 nm) by the total number of base pairs in a diploid cell (~6.3 billion).

According to a 2019 study published in the Annals of Human Genetics, the male nuclear diploid genome measures 205.00 cm in length, while the female genome extends to 208.23 cm due to the larger second X chromosome compared to the Y chromosome.

MeasurementMaleFemaleMean
Base pairs (Gbp)6.276.376.32
Length (cm)205.00208.23206.62
Weight (pg)6.416.516.46

Despite measuring over 2 meters, this DNA fits inside a cell nucleus only 5–10 micrometers (μm) in diameter—a compaction ratio of roughly 10,000:1. This remarkable feat is achieved through hierarchical packaging involving histone proteins that coil DNA into increasingly compact structures called chromatin.

How long is DNA stretched out in the human body?

The total length of DNA in an adult human body is approximately 6.2 billion kilometers (3.9 billion miles). This calculation uses the latest estimate of 3 × 10¹² nucleated cells per human body, each containing about 2.07 meters of DNA.

To put this astronomical distance in perspective:

  • 41× the Earth-Sun distance (which is 150 million km)
  • Enough to reach Neptune and back from the Sun
  • Roughly twice the diameter of our Solar System

The estimate specifically counts nucleated cells because red blood cells—which make up about 70% of all cells by number (~25 trillion)—lack nuclei and therefore contain no DNA. The remaining ~7 trillion nucleated cells include white blood cells, skin cells, muscle cells, and other tissue cells that retain their genetic material.

How long is each chromosome?

Human DNA is organized into 46 chromosomes (23 pairs), ranging dramatically in size. Chromosome 1 is the largest, while chromosome 21 is the smallest.

ChromosomeBase pairs (Mbp)Length (cm)
1 (largest)2498.14
22427.92
31986.47
X1565.10
Y571.86
21 (smallest)471.53

Chromosome 1 alone contains about 8% of the total human genome and encodes approximately 2,200 genes. When fully stretched, it would span about 8 cm—yet it must compress to fit within the microscopic confines of the nucleus alongside 45 other chromosomes.

DNA double helix dimensions

The DNA double helix has remarkably consistent physical dimensions:

ParameterValue
Diameter2 nm (20 Å)
Base pair spacing (rise)0.34 nm (3.4 Å)
Base pairs per turn10–10.5
Helical pitch3.4 nm (34 Å)

These measurements apply to B-DNA, the most common form found in cells under physiological conditions. The consistent 2 nm diameter results from the nearly identical geometries of A:T and G:C base pairs, allowing them to stack uniformly along the helix.

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